Quadrature modulators used in communication systems receive quadrature inputs x1 and xQ which are modulated up to a carrier frequency ωc. The quadrature modulator operates by mixing the in-phase input signal, x1, with cos(ωc+φ) and quadrature-phase input signal xQ by sin(ωc−φ) and summing together the two mixed signals. Generally the error, φ, is regarded as a function of the carrier frequency ωc. But it has been determined that the error φ is also a function of the frequency of inputs x1 and xQ and further that as the input signal bandwidth x1, xQ becomes larger, there is more variation in the error φ across the band. Thus the conventional approach of assuming phase error φ is constant across the input signal frequency band and nulling out phase error φ, by pre-compensating for a constant phase error is not truly sufficient. The gain imbalance (frequency dependent or otherwise) and local oscillator feed-through due to dc-offset in the I and Q paths are assumed to be taken care of by other means and are not addressed here. These gain and dc-offset terms are hence not shown or discussed in the rest of the disclosure.